Prudent management of lotic systems requires information on their ecological status that can be estimated by monitoring water quality and biodiversity attributes. To understand environmental conditions in Gatharaini drainage basin in Central Kenya, a study was carried out to establish the relationship between water quality and macroinvertebrate assemblages between the months of March and September 1996. Six sampling sites, each 25 m long were selected along a 24-km stretch of the stream, which drained land under agricultural, residential and industrial use. Water physico-chemical data was explored using multivariate analysis of Principal Component Analysis to detect environmental trends downstream. Both macroinvertebrates and water physico-chemical data of suggested trends were analysed for variations and correlations. Temperatures and invertebrate densities changed significantly between the dry and wet season (P < 0.01) but the fluctuations were not evident downstream. Water physico-chemical characteristics (total dissolved solids (TDS), pH, turbidity, dissolved oxygen) and biodiversity indices (species richness, diversity, dominance, evenness) changed markedly downstream (P < 0.01). Biodiversity indices correlated inversely with TDS, pH and turbidity but positively with dissolved O 2 . It was evident macroinvertebrate assemblages changed significantly downstream as opposed to functional feeding groups. Diptera was important in most sites whilst Oligochaeta dominance increased downstream corresponding to the deterioration in water quality. Collectors/browsers were the dominant functional feeding groups at most sites. This study showed that significant changes in aquatic macroinvertebrate assemblages were primarily due to water quality rather than prevailing climatic conditions. collecteurs/brouteurs constituaient les groupes d'alimentation dominants sur la plupart des sites. Cette étude a montré que les changements significatifs dans les assemblages de macro-invertébrés aquatiques étaient dus plutôt à la qualité de l'eau qu'aux conditions climatiques.Water quality and macroinvertebrate assemblages 209 Ó

In the arid and semiarid lands (ASAL) of Kenya, fuelwood and charcoal constitute 95–98% of the total energy demand for cooking, heating and lighting. The resultant deleterious ecological effects are severe and need urgent remedial interventions. A study was carried out in Marsabit District, which is a vast ASAL region, to examine the effects of woodfuel consumption on Marsabit Forest and the surrounding areas. It was found that wood for fuel harvested from Marsabit Forest was approximately 56,000 tons y−1. The rate of deforestation was estimated at 1.6 ha y−1. This resulted in great loss of indigenous biodiversity, destruction of vital ecosystems and habitats. To control further degradation of the forest, it is recommended that an immediate ban be imposed to stop harvesting of the indigenous species such as Olea spp. and Teclea spp., which are seriously endangered. Also, woodfuel conservation through wider and more efficient use of the improved energy‐saving technologies should be enhanced.

In the semi-desert zone of North Horr, northern Kenya, soil salinity reaches toxic levels, with extensive salt crusts at the surface. Environmental groups are involved in tree and shrub planting trials with the objective of stabilizing sand dunes and rehabilitating land. However, the performance of the various indigenous and exotic tree and shrub species in rehabilitating these saline soils has not been examined. Therefore this study aimed at evaluating the performance of various exotic and indigenous tree and shrub species in rehabilitating saline soils in North Horr. Mortality and relative growth rates for both exotic and indigenous tree and shrub species were assessed. Compared to indigenous species, exotic tree species (not naturally growing in the Marsabit ecosystem) failed to sustain an improved growth performance in saline soils of North Horr. The results of this study demonstrate that survival rates for indigenous plants in North Horr are higher than those of exotic ones. Thus, to rehabilitate saline soils and stabilize sand dunes, the use of indigenous tree and shrub species adapted to such saline conditions should be encouraged.

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The biodiversity characteristics in eight small (0.065-0.249 km 2 ) public man-made reservoirs in the central part of the Eastern Rift Valley, Kenya, were studied between 1995 and 1998. A total of 71 phytoplankton species belonging to approximately 50 taxa were identified. Chlorophytes and cyanobacteria dominated the crop. The dominant taxa included Botryococcus, Syunura, Microsystis, Anabaena, and Cosmarium. A total of over 40 zooplankton species were identified. The community was composed mainly of crustacea, rotifers and protozoa. The most dominant group was Keratella but Brachionus and Nauplius were equally abundant. The diversity and abundance of benthic invertebrates was not high, and only 18 species were identified throughout the study period with the range of species number being 1-7 per reservoir. The benthic fauna was mainly composed of Lumbriculidae and Chironomid worms. A total of six monthly bird counts found an average of 60 birds per reservoir, and a total of 49 species was identified. Ducks, geese and coots dominated the waterfowl, especially during the dry season. Largescale breeding by Black-headed Heron (Ardea melanocephala) and Little Egret (Egretta garzetta) was observed in one of the sites, and other species were also breeding in the reservoirs. The population of waterbirds in reservoirs was closely related to the biomass of benthic invertebrates, and the findings of the study indicate that the structure and dynamics of life forms within small man-made reservoirs can serve as excellent sensors and indicators of the state of watershed health.